Binding of a TlCl Entity by a Tetragold Tetramercaptothiacalixarene Metalloligand via Metallophilic Interactions.

The successive auration of p-tert-butyltetramercaptotetrathiacalix[4]arene, H4 (MTC[4]), with gold(I) phosphine units was investigated. Through deprotonation with NaOMe, followed by salt metathesis reactions with (PR3 )AuCl (R=Me, Ph) complexes with two and three [(PR3 )Au]+ moieties could be prepared and isolated, namely [(Ph3 PAu)2 H2 (MTC[4])] and [(Me3 PAu)3 H(MTC[4])]. In [(Me3 PAu)3 H(MTC[4])] two gold atoms already come close enough to undergo aurophilic interactions. To introduce a fourth [(PR3 )Au]+ entity TlOEt had to be used for the deprotonation, which led to the finding that four gold atoms organised by the (MTC[4])4- coordination platform are able to bind and stabilize a TlCl entity, yielding [(Me3 PAu)4 TlCl(MTC[4])]. As evidenced by structural and theoretical investigations the binding occurs through strong metallophilic interactions, which lead to photoluminescence at low temperatures.

Quinone-annonaceous acetogenins: synthesis and complex I inhibition studies of a new class of natural product hybrids.

The natural product hybrids quinone-mucocin and quinone- squamocin D were synthesized. In these hybrids, the butenolide unit of the annonaceous acetogenins mucocin and squamocin D is exchanged for the quinone moiety of the natural complex I substrate ubiquinone. For both syntheses, a modular, highly convergent approach was applied. Quinone-mucocin was constructed out of a tetrahydropyran (THP) component 1, a tetrahydrofuran (THF) unit 2, and a quinone precursor 3. A stereoselective, organometallic coupling reaction was chosen for the addition of the THP unit to the rest of the molecule. In the final step, the oxidation to the free quinone was achieved by using cerium(IV) ammonium nitrate (CAN) as the oxidizing agent. Quinone-squamocin D was assembled in a similar manner, from the chiral side chain bromide 16, the central bis-THF core 17, and the quinone precursor 18. Inhibition of complex I (isolated from bovine heart mitochondria) by the quinone acetogenins and several smaller building blocks was examined; quinone mucocin and quinone-squamocin D act as strong inhibitors of complex I. These results and the data from the smaller substructures indicate that other substructures of the acetogenins besides the butenolide group, such as the polyether component and the lipophilic left-hand side chain, are necessary for the strong binding of the acetogenins to complex I.

Fístulas arteriovenosas braquiocefálicas e braquiobasílicas para hemodiálise: seguimento precoce e tardio / Brachiocephalic and brachiobasilic arteriovenous fistulas for hemodialysis at the early and late follow-up

Entre junho de 1985 e setembro de 1992 foram realizadas 78 fístulas arteriovenosas em pacientes portadores de insuficiência renal crônica terminal, distribuídas em dois grupos: 59 fístulas do tipo braquiocefálica, realizada em 54 pacientes, e 19 fístulas do tipo braquiobasílica com superficializaçäo da veia basílica, executadas em 18 pacientes. Os grupos foram estudados em dois períodos distintos - seguimentos precoce e tardio - e analisados em funçäo da perviedade e das complicaçöes. Os resultadosbtdiso permitem concluir que ambas as técnicas säo alternativas válidas para a manutençäo de pacientes com insuficiência renal crônica terminal em programa de hemodiálise, especialmente quando näo há condiçöes de realizaçäo ou de preservaçäo de acesso na altura do antebraço, pois apresentam poucas complicaçöes e alto índice de perviedade no seguimento tardio.